Sectional mandrel



Patented Sept. 22, 1931 g `Uhuru-D i'sra'riis PATENT oFFICE' RICHARD SCHROEDR, or BEnLiN-wErssENsEn fefitaiimlym Lsno'riolvnr. MANDREI.

Application led February 25, 1927, ASerial No. 170,931, andv in Germany March 5, 1926. i

5 of iexible fibrous or textileymaterial which has been preferably submitted to a previous treatment with natural or artificial resins or gums are placed upon'a metallic mandrel by a winding operation with'the simultane- 10 ous employment of pressure and heat, the

outer dimensions of such mandrel corresponding to the desired interior' dimensions of the` cylinders to be obtained.` In the manufacture of such .cylinders which are,

F 15 for instance, used for insulatingpurposes,

thereiarises the difficulty that the outer surfaceof the mandrels which are ordinarily .or intermediate pieces of substantially holmade of cast iron or wrought iron, mustV be very carefully prepared; the mandrel must be very accurately and smoothly turned off, for instance, and must be subsequently ground and polished, soasto yield an entirely unobjectionable product. This ,treatment renders such mandrels of course very expensive, particularly so, because the thickness of the walls of the mandrelsi must be quite considerable on account of thefgreat compressivek strain during thewinding operation. It would., therefore, entail excessive costs, and moreover would require an undue amount of space for the manufacturerv to keep a large amount of mandrels in stock to correspond'to all possible inner diame- V ters of such insulating cylinders or the like, even-.for the sizes rarely used. It has, therefore, been suggested toy manufactureinsulating cylinders of other interior diameters thanthe standard size and to usemandrels of standard diameters and firstlyv mount an insert or intermediate layer upon the winding mandrel of the next smallest size available, so asl to enlarge the'mandrel to the desired interior diameter, the insulating cylinder proper being then wound upon v'said intermediate insert. Such inserts were usually either manufactured from unvarnislied paper, in which case the result was unsatisfactory, or the insert was made vfrom the same raw material as the insulating cylinder, for instance, of varnished orjapanned paper.

pose whichare made of substantially-dur-v These inserts had to kvbe subsequently peeled out or withdrawn from-the finished insulating cylinders, or the like, and wereus'ually thrown away, because only rarely couldA the insert be withdrawn fromthe finished in- Y .which may be used almost indefinitely and which present theradditional advantage of easy manipulation, and'agreat reductionin the costs of storage, combined with highly 65 satisfactoryV results -inf the Vwound material.

In accordance with this` invention, inserts low cylindrical shape are used-for this purable material and which are split or slit along a line running longitudinally on their outer surface, or approximately along such line, the slit extending in the radial direction or in a, direction at an angle to the` 4radial plane. Such hollow cylinders are mounted upon the mandrel either singlyor superimposedly, and after having been surrounded with the wound layers of material, and after said layers have been baked, they vE30 are Withdrawn from the mandrel together with the wound cylinder. From the finished insulating cylinder the inserts referred to may be easily withdrawn, without any danger of injuring the inner walls `of the v'85 finished cylinders because ofthe resiliency and elasticity of the insert produced by the slittinglthereof and because of they use of some suitable means lto prevent sticking of the innerlayer of the hollow cylinder to the outer face of the mandrel in the eventthe 4materiall from which the hollow cylinder is andresin, particularly artificial resin, and

'they are split open after having been dried dierences of diameter (0.8 inch `to 1%' inch), while for obtaining the intermediate diameters slitted insertsare provided With about 2 to 5 millimeters thickness of'walls which are placed upon each other, untilthe desired interior diameter has been obtained.

The invention Will nowbe described with -reference tothe accompanying drawings,

V showing, by way-of example, mandrels in accordancewith thisv invention with cylinders produced by the Winding thereon of layers of fabric, or the like. 'Figure V1 is a cross sectional viewiof a winding mandrel' lof the kind described with an insert mounted thereupon, Vand withan insulating cylinder Woundvaround said insert. Figure 2 illustrates the insert and the insulating cylinder.y corresponding to Figure 1, showing .them Withdrawn 'from the Winding mandrel Y together. FigureBishows, byvway lof eX- emplification inV perspective a winding inanldrel andjthreesuperimposed inserts and an insulating cylinderV wound thereon, large pieces of different sizes'being shown cut out or broken out from the insulating cylinder and-from the three inserts for the sake lof' `clearness ofv illustration. Figure 4 is a vcross-section through the mandrel with the inserts and the cylinder according to F ig In Figure 1 of the drawings, 1 .indicates the Winding mandrel which in this particular embodiment may have a` dia-meter of say 500 millimeters or about inches, 2 is the product obtained by the winding opera- 'tion which in this particular insta-nce may ocomprise a cylinder of an interior diameter of sheets of impregnated paper, andadapted of 505 millimeters obtainedby the winding for subsequent baking, 3 is the insert, or intermediate layer, which-serves for the increase of the diameter of the mandrel so as to be equal jto the inner diameter of the finished cylinder. The insert, according to a preferred embodiment of the invention,

vcomprises a cylinder of hard paper of 500 -millimeters interior diameter and 21/2 millivmeters. thickness of wal1s,that is to say with an outer diameter of 505 millimeters, which is equal to the inner diameter of the finished cylinder. The insert is slitted along a line 4 at an inclination to the radial plane. In Figure 2 the finished cylinder is indicated at 2, 3 being the insert still housed therein, While the mandrel 1 has been removed.

In the modification according to Figures 3 and 4, the winding mandrel is likewise indicated at l as in Figure 1, that is to say, it is'supposed to have a diameter of 500 millimeters; 2. is the finished cylinder which in this case, however, has a diameterof 515 millimeters, sothat an annular space of 71/2 millimeters width in the radial direction remains between the mandrel andthe cylinder. rlhis space is occupied by three inserts, or intermediate layers 31, 32, 33, each having walls ofV 21/21millimeters thickness, and of which the innermost insert has an` inner -diameter of 500 millimeters, the next one an interior diameter of 505 millimeters, and the exterior or third insert havingV an interior diameter of 510 millimeters. Each of said inserts is split open along a line ati` ranged.' The winding mandrel 1 with thei three inserts is therefore a-dapted for the winding of cylinders ofl 500, 505, 510, and 515 millimeters interior diameter. After the cylinder has vbeen wound on the mandrel comprising the member 1 and oneor more oi?- the mandrel elements or inserts engaged thereover, the mandrel: l is first withdrawn, and' then the inserts can be easily removed one after the other. In thisv connection it is pointed out that in forming any given insert? or. mandrel element, or insulating cylinder,

by winding resin impregnated paper or the like on the mandrel 1, or onl a mandrel element or insert previously formed, sticking of the inner layer of the mandrel yelement or insulating cylinder being formed to the outer face of the mandrel 1 or to a mandrel element engaged thereover, as the case may be, may be prevented in any oneaof three practicable ways; viz., by applying to the? outer faceA of the mandrel or mandrel element, as the case may be, a suitable lubricant; by placing a thin sheet of unimpregnated paper or other material around the ment before beginning to wind the impreg- -nated material thereon; or, by employing paper or the like which is treated on only one `face with resin, lacquer, varnish or the like and `disposing the untreated side loithe paper towards the mandrel.

v It should, of course, be understood lthat the invention is by no means restricted to cylinders, but is applicable to other crossv sectional shapes asl Well, particularly to the shapes usually employed for electro-'technical purposes, for instance, four-cornered, square and oval shapes, and while the invenouter face of the mandrel or mandrel ele-V izo tion has been shown and described herein in y.

`connection -with'what may be considered its' preferred embodiments, it Will be evident that it is susceptible of other modiiications and changes in accordance With varying conditions of application Without departing from the spirit and scope of the invention, as

deiined in the claims hereunto appended.

I claim l. A sectional mandrel for use as a core in producing hollow bodies comprising aplurality of mandrel elements in the form of sleeves adapted for engagement one over another to provide a core of a desired diameter, each sleeve comprising ra strip of flexible material Wound in superimposed layers and longitudinally slit, the smallest sleeve corresponding in interior cross sectional size and shape to a mandrel over Which saidA sleeve is adapted to be engaged, and each successively larger sleeve corresponding in interior size and shape to the exterior sizeand shape of the sleeve next smaller in size.

2. A sectional mandrel for use as a core in producing hollow bodies, comprising an inner mandrel element and an outer man-` drel element engageable over said inner mandrel element to increase the eii'ective diameter of the mandrel, saidouter mandrel ele ment being in the form of a longitudinal slit sleeve composed of superimposed layers of flexible material. Y

3. A sectional mandrel Jfor use as a core in producing hollow bodies, comprising an inner mandrel element and an outer mandrel element engageable over said inner rmandrel element to increase the effective diameter of the mandrel, said outer mandrel element being in the form of a longitudinal slit sleeve composed of superimposed layers of flexible material, said sleeve corresponding interiorly in cross sectional size and shape to the exterior cross sectional size and shape of the inner mandrel element.

In testimony whereof I ax my signature.

RICHARD SCHROEDER. 

